1. Field of the Invention
The present invention relates to a faulty operation prevention circuit for an infrared-ray remote controller, which is disposed in a system body receiving a transmission signal from the infrared-ray remote controller.
2. Description of the Prior Art
Recently, in systems such as a microcomputer, a television receiver, an audio set, an air conditioner and the like, an infrared-ray remote controller has been provided to remotely control power ON/OFF, channel selection, volume adjustment etc. of the corresponding system (a system body). Generally, a transmitter of the infrared-ray controller transmits successively an infrared-ray signal in the form of digital information of "1" and "0" and a receiver of the system body receives the successive digital information from the transmitter of the infrared-ray remote controller, decodes the received digital information and controls the associated components of the system body in accordance with the decoded result.
However, various noise sources such as a fluorescent lamps and others may be present in the vicinity of the infrared-ray remote controller. For this reason, the transmission signal from the infrared-ray remote controller may be mixed with a noise of a level higher than a predetermined level. In this case, the digital information decoded in the receiver of the system body may be different transmitted by that from the infrared-ray remote controller. This results in a faulty operation of the system body.
FIG. 4 is a data format of the transmission signal from the infrared-ray remote controller and FIG. 5 is a data format of the transmission signal in FIG. 4 in which an optical noise is contained. As shown in these drawing, the transmission signal includes a START bit, CODE bits C1-C3, a SECOND bit, DATA bits A-E, an END bit and 4 redundancy bits.
FIG. 6, illustrates a schematic block diagram of a conventional remote control reception apparatus. As shown in this drawing, the conventional remote control reception apparatus comprises a remote control receiver 1 disposed in the system body. The remote control receiver 1 is adapted to receive the transmission signal (a remote control signal) from the infrared-ray remote controller, decode the received remote control signal and output the decoded signal to the associated components in the system body. For example, the remote control receiver 1 outputs the decoded signal in the form of pulse code to a microcomputer (not shown) in the system body. The microcomputer performs a proper operation based on the pulse code signal from the remote control receiver 1. As stated previously, the transmission signal from the infrared-ray remote controller may be mixed with the optical noise as shown in FIG. 5.
However, noise prevention means is not disposed at the output of the remote control receiver 1 in the remote control reception apparatus in FIG. 6. For this reason, in the case where the optical noise is mixed with the transmission signal from the infrared-ray remote controller as shown in FIG. 5 under the condition that the pulse code signal from the remote control receiver 1 is "0", the microcomputer recognizes the pulse code signal of "0" as "1". As a result, the faulty operation of the system body is caused. Noticeably, the detection of "H" and "L" levels ("1" and "0" levels in FIG. 5) of the transmission signal from the infrared-ray remote controller is repeatedly performed several times. With the optical noise mixed with the transmission signal in such a detection operation, the "L" level of the transmission signal may be detected as the "H" level.